1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4.. _VIDIOC_G_CROP: 5 6********************************** 7ioctl VIDIOC_G_CROP, VIDIOC_S_CROP 8********************************** 9 10Name 11==== 12 13VIDIOC_G_CROP - VIDIOC_S_CROP - Get or set the current cropping rectangle 14 15Synopsis 16======== 17 18.. c:macro:: VIDIOC_G_CROP 19 20``int ioctl(int fd, VIDIOC_G_CROP, struct v4l2_crop *argp)`` 21 22.. c:macro:: VIDIOC_S_CROP 23 24``int ioctl(int fd, VIDIOC_S_CROP, const struct v4l2_crop *argp)`` 25 26Arguments 27========= 28 29``fd`` 30 File descriptor returned by :c:func:`open()`. 31 32``argp`` 33 Pointer to struct :c:type:`v4l2_crop`. 34 35Description 36=========== 37 38To query the cropping rectangle size and position applications set the 39``type`` field of a struct :c:type:`v4l2_crop` structure to the 40respective buffer (stream) type and call the :ref:`VIDIOC_G_CROP <VIDIOC_G_CROP>` ioctl 41with a pointer to this structure. The driver fills the rest of the 42structure or returns the ``EINVAL`` error code if cropping is not supported. 43 44To change the cropping rectangle applications initialize the ``type`` 45and struct :c:type:`v4l2_rect` substructure named ``c`` of a 46v4l2_crop structure and call the :ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` ioctl with a pointer 47to this structure. 48 49The driver first adjusts the requested dimensions against hardware 50limits, i. e. the bounds given by the capture/output window, and it 51rounds to the closest possible values of horizontal and vertical offset, 52width and height. In particular the driver must round the vertical 53offset of the cropping rectangle to frame lines modulo two, such that 54the field order cannot be confused. 55 56Second the driver adjusts the image size (the opposite rectangle of the 57scaling process, source or target depending on the data direction) to 58the closest size possible while maintaining the current horizontal and 59vertical scaling factor. 60 61Finally the driver programs the hardware with the actual cropping and 62image parameters. :ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` is a write-only ioctl, it does not 63return the actual parameters. To query them applications must call 64:ref:`VIDIOC_G_CROP <VIDIOC_G_CROP>` and :ref:`VIDIOC_G_FMT`. When the 65parameters are unsuitable the application may modify the cropping or 66image parameters and repeat the cycle until satisfactory parameters have 67been negotiated. 68 69When cropping is not supported then no parameters are changed and 70:ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` returns the ``EINVAL`` error code. 71 72.. c:type:: v4l2_crop 73 74.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}| 75 76.. flat-table:: struct v4l2_crop 77 :header-rows: 0 78 :stub-columns: 0 79 :widths: 1 1 2 80 81 * - __u32 82 - ``type`` 83 - Type of the data stream, set by the application. Only these types 84 are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``, ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``, 85 ``V4L2_BUF_TYPE_VIDEO_OUTPUT``, ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE`` and 86 ``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :c:type:`v4l2_buf_type` and the note below. 87 * - struct :c:type:`v4l2_rect` 88 - ``c`` 89 - Cropping rectangle. The same co-ordinate system as for struct 90 :c:type:`v4l2_cropcap` ``bounds`` is used. 91 92.. note:: 93 Unfortunately in the case of multiplanar buffer types 94 (``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` and ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``) 95 this API was messed up with regards to how the :c:type:`v4l2_crop` ``type`` field 96 should be filled in. Some drivers only accepted the ``_MPLANE`` buffer type while 97 other drivers only accepted a non-multiplanar buffer type (i.e. without the 98 ``_MPLANE`` at the end). 99 100 Starting with kernel 4.13 both variations are allowed. 101 102Return Value 103============ 104 105On success 0 is returned, on error -1 and the ``errno`` variable is set 106appropriately. The generic error codes are described at the 107:ref:`Generic Error Codes <gen-errors>` chapter. 108 109ENODATA 110 Cropping is not supported for this input or output. 111